Well I stumbled into a job working from home entirely by accident. I'd been applying to all sorts as I just needed the work, but it was the work from home one that ended up hiring me. Which obviously worked out pretty well for me given how much I try to avoid dealing with other people.
Anyway, it basically entails looking after various message boards and chatrooms. It's surprising just how many companies will pay another company to come in and do this kind of work for them. Because of the nature of the work, aside from the odd training session, pretty much everything can be done from home. The pay isn't fantastic (above minimum wage though), but that is offset by the lack of costs for things like travel and the such.
I'd guess there are other, similar jobs out there as well, and I'd guess that it's becoming increasingly common for jobs to be carried out from home, but that's the only experience I have of it. It certainly suits someone like myself though, and I couldn't ever see myself doing something like a 9-5 office job.